The present invention relates to a pipe coupling consisting of male and female couplers or couplings, and, in particular, to a female coupler.
In recent years, hydrogen-powered vehicles have been developed and put to practical use. To supply such vehicles, it is necessary to provide liquid hydrogen in tanks at gas stations or the like. To transfer liquid hydrogen from a supply tank at a gas station of the like to a vehicle tank, a female coupler fluidly connected to the hydrogen supply tank is joined to a male coupler fluidly connected to the vehicle tank.
The liquid hydrogen is stored under high pressure, for example, at a pressure of around 30 Mpa or more. Thus, a female coupler to be used in transferring liquid hydrogen under such high pressures must have a sufficiently strong construction. In providing a female coupler which has a sufficiently strong construction, however, the coupler inevitably becomes both bulky and heavy, which makes it difficult to be used by either a driver, or by an attendant at a gas station.
Further, the conventional type of female coupler is designed such that when a male coupler has been adequately inserted into a tubular body of the female coupler, a sleeve slidably mounted on the tubular body is moved to a locking position under the action of a spring which radially inwardly forces locking balls provided in the tubular body into an annular groove of the male coupler, to thereby securely hold the male coupler within the female coupler. However, there is a danger with this construction that the male coupler may suddenly become disengaged and move out from the female coupler before the annular groove reaches a position for receiving the locking balls. While sudden movement of the male coupler may cause the sleeve to be moved by the spring to the locking position, if the male coupler is slowly pulled out, an inner movable member or locking ball support member provided in the tubular body, which has been moved rearwards against a second spring by the male coupler, will be returned under the action of the second spring, and will support the locking balls to prevent the sleeve from moving to the locking position. A female coupler which is subject to a high pressure fluid such as liquefied hydrogen is desirably designed to associate the sleeve with a valve provided in the female coupler such that only when the sleeve is located at a locking position, which means a male coupler has been connected to the female coupler by means of the locking balls, the valve is allowed to be opened. It is therefore desirable for such a female coupler to be able to prevent the sleeve from accidentally moving to the locking position in a situation that the male coupler suddenly becomes disengaged and moves out from the female coupler before the annular groove of the male coupler reaches a position for receiving the locking balls.